The present invention relates generally to electrical connectors, and more particularly to high speed connectors utilized in edge connector applications having multiple circuit paths to increase the electrical performance thereof.
Electronic devices being manufactured today are operating at faster performance speeds than past devices. Such devices, especially computing devices, in order to compute in today""s technological environment, need to have the capability of performing data transfer at high rates. While electronic devices, such as laptop and other portable computers are being reduced in size, so too, are their electronic components being asked to function at higher speeds and rates, but within smaller spaces. The competitiveness of today""s marketplace places pressure on electronic manufacturers to decrease the size of their components, while increasing the efficiency thereof. This effect impacts the suppliers of components to these manufacturers. In particular, there is pressure on connector manufacturers to reduce the size of connectors while increasing the data throughput of the connector. As the size of a connector is decreased, the connector must function at a high rate and with a decrease in the inductance of the connector.
Although short and thick conductive terminals may provide lower inductance, they may not maintain their contact flexibility in a manner that would enhance their ability to mate with circuit boards and to meet the reduced pitch required for high density connectors. Terminals with greater flexibility typically include long and slender contact beams. Although such terminals may function adequately to provide a connection between the edge card contacts and the circuit board contacts, they may possess a high inductance. Inductance for the most part depends on the physical characteristics of the terminal.
Shortening of the circuit path of the terminal improves the performance of the terminal by lowering the inductance. Providing dual contacts on the base portion of the terminals, such as a solder tail on one part of the terminal and a surface mount foot on another part of the terminal, will also reduce the inductance of the terminal. Increasing the length of the terminal contact arms as is often necessary in multi-level edge card connectors for lower insertion force, will result in an increase in the inductance of the terminal that effectively will cancel out the reduction obtained by using dual contacts on the base of the terminal.
A need therefore exists for a high-speed, edge card connector having an improved electrical performance in which the inductance of the connector is reduced, without comprising the mechanical operation of the contact portions of the connector terminals.
It is therefore an object of the present invention to provide an improved edge card connector for use in high speed applications with reduced inductance.
Another object of the present invention is to provide an edge card connector having a plurality of terminals with minimal inductance without diminishing the mechanical performance thereof and further electrically coupled to improve the performance of the terminals.
Still another object of the present invention is to provide an edge card connector for high speed applications in which the connector includes a plurality of conductive terminals arranged on opposite sides of a card slot of the connector, the terminals being of at least two distinct types: a signal type and a ground type, the signal and ground-type terminals being alternatingly arranged lengthwise of the connector, the grounding type terminal having a pair of contact beams formed thereon, one of the pair of contact beams being deflectable into contact with the other of the contact beams upon insertion of the circuit card into the card-receiving slot.
Yet a further object of the present invention is to provide a connector having a plurality of terminals arranged on opposite sides of a connector slot, some of the terminals having a dual circuit path defined by a pair of contact beams formed therewith that are cantilevered vertically from a base portion of the terminals, one of the beams being deflectable into contact with the other to provide an additional circuit path for current or ground along the length of the terminal.
A still further object of the present invention is to provide an edge card connector suitable for high-speed applications in which the connector includes an elongated insulative connector housing, a card-receiving slot disposed within the connector housing and extending longitudinally therein, a plurality of conductive terminals arranged within the connector housing and disposed in pairs on opposite sides of the card-receiving slot, some of the terminals being signal terminals and other of the terminals being reference or power terminals, the reference or power terminals having a pair of contact arms that are movable into engagement with each to short the terminals in order to provide dual electrical paths upon insertion of a circuit card into the connector card-receiving slot, at least one of the contact arms being deflectable into contact with the other under urging of the circuit card.
Yet still another object of the present invention is to provide a high-speed connector having a selected set of conductive terminals that are capable of shorting themselves when a circuit card is inserted into a card slot of the connector, each of the selected terminals having primary and secondary contact members that take the form of cantilevered beams having free ends that are spaced apart from each other a distance that is generally less than the amount of deflection undergone by one of the two contact members when the circuit card is inserted such that when a circuit card is inserted into the card slot of the connector, one of the contact members is urged into sliding engagement with the other of the two contact members, the free ends thereof having cam surfaces that engage and slide along each other in order to define two distinct circuit paths within said terminal extending between the circuit card contacts and contacts on a circuit board.
A still further object of the present invention is to provide an improved circuit card connector particularly suitable for high speed applications having a plurality of signal terminals and a plurality of reference or power terminals arranged on both sides of a circuit card-receiving slot of the connector, the reference or power terminals having a pair of upright contact beams in opposition with each other and aligned for shorting contact with each other, one of the contact beams protruding partially into the card-receiving slot and deflecting into contact with the other contact beam when a circuit card is inserted into the card-receiving slot. The two contact beams have opposing free ends that slidingly engage each other due to urging of the circuit card when it is inserted into the card-receiving slot, the two contact beam free ends deflecting sideways a distance between one-half and one full material thickness of the contact beams, thereby establishing a shorting contact between the two beams without substantially or materially increasing the circuit card insertion force.
The present invention achieves these objects through a unique terminal structure in which selected terminals are provided with a pair of opposing spring arms that are spaced apart from each other at the tops of the terminals. One of the spring arms extends into the card slot and is deflectable rearwardly into its terminal-receiving cavity. The two spring arms are vertically cantilevered and extend up from a body portion of the terminal so that an edge of the circuit card will deflect the one spring arm into sliding contact with the other spring arm in order to define a second circuit path of the terminal through the other spring arm that deflects less than the spring arm that extends into the card slot. These two circuit paths improve the electrical performance of the connector by lowering its inductance.
When the free ends of the two spring arm portions contact each other, two parallel electrical paths are created. It is known that inductance of a terminal is dependent upon the length of the circuit path that extend through a terminal. The longer the circuit path, the greater the inductance. The spring arms of the present invention contact each other at the tops of their associated terminals to create an electrical short between the two spring arms to thereby define two distinct circuit paths that extend through the terminal. These circuit paths are preferably the same length. Each such circuit path will generate a given inductance, while the two spring arms act as a pair of inductors in parallel when contacted against each other and thereby generate an inductance that is lower than the actual inductance of either of the two spring arms alone.
The parallel circuit paths defined by the two spring arms of these selected terminals help keep the inductance of the selected terminals low. In order to further enhance the electrical performance of these selected terminals (as well as that of other terminals), the selected terminals may be provided with an area of enlarged surface area that promotes electrical coupling with adjacent terminals.
The free ends of the spring arm portions preferably include cam surfaces, which in one embodiment of the invention include angled surfaces, that slidingly engage each other when the circuit card is inserted into the card slot. Circuit cards may be manufactured to certain tolerances in which warpage of the circuit card may occur which may affect the connector structure. In order to counter such warpage, it is desirable to increase the extent of the one spring arms into the connector card slot. If the two spring arms were to meet face to face under application of a circuit card, a combined, larger force is generated to insert the circuit card, which increases the insertion force required for the circuit card. By providing cam surfaces at the free ends of the spring arms, and by providing them not only away from the connector housing slot, but also above the level of the card contact portions of the terminals, a minimal increase is achieved in the normal force required for insertion of the circuit card into the connector card-receiving slot and a small gap between the free ends and cam surfaces may be attained so that a reliable engagement may be had with as little as five-thousandths (0.005 inches) deflection.
The engagement of these two free ends is in a sliding, or frictional contact, type of engagement. This sliding action is oriented generally perpendicularly or transverse to a longitudinal axis of the connector housing card-receiving slot. The sliding contact in this direction leads to a maximum deflection of the contact beam being the material thickness of the contact beam and a minimum deflection of the same is about one-half a contact beam thickness.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.